Radio frequency transformer and coil form



June 19, A, WILLYARD ETAL RADIO FREQUENCY TRANSFORMER AND COIL. FORMFiled June 20, 1952 m I cull: 50 lg 58 Vl/l/l/l/lAIIIIIIII V/l/IYI/A Mar56 INVENTOR$ BY WM ORNEY United States Patent RADIO FREQUENCYTRANSFORMER AND COIL FORM Leslie A. Willyard, Inglewood, and Ingemar R.V. Taegtstroem, Los Angeles, Calif.; said Taegtstroem now by change ofname Ralph Textrom; assignors to Hoffman Electronics Corporation, LosAngeles, Calif., a corporation of California Application June 20, 1952,Serial No. 294,618

8 Claims. (Cl. 336-65) This invention relates to radio apparatus, andparticularly to an improved coil form or transformer unit which hasspecial advantages for high frequency applications.

A principal object of the invention is to provide a unit of this typewhich simplifies the manufacture of single and double wound radiofrequency coils for accurate control of their electricalcharacteristics, and in which interchangeable parts are employed toreduce cost and simplify construction.

A further object of the invention is to provide a unit of the above typeincluding improved means for maintaining in adjusted position a magnetictuning slug or the like, so that the adjusted value of inductance willnot vary during operation as a result of shocks, vibration and the like.

An additional object of the invention is to provide a coil form havingarrangements whereby the electrical leads from its winding or windingsmay be accurately placed and maintained with'respect to other circuitcomponents; this feature is especially important for operation at veryor ultra high frequencies, where lead dress, or the proper positioningof the various conductors, may have considerable importance withrelation to circuit tuning, efficiency and so on.

Still another object of the invention is to provide a structure havingthe above characteristics and which can be of very small size withoutunnecessary sacrifice of ruggedness; this feature, again, is ofparticular importance in connection with the higher radio frequencies,and especially so where the equipment as a whole is to be extremelysmall and compact, because the mere scaling down of conventional designsfor larger size transformers and coils results either in a sacrifice ofstrength, or leads to manufacturing ditficulties.

The above and other objects and advantages of the invention will best beunderstood by referring to the following detailed specification of apreferred embodiment of the invention, and of a modification thereof,taken in connection with the appended drawings, in which:

Fig. 1 is a view in elevation of a radio frequency transformer embodyingthe invention, a part being broken away for clarity,

Fig. 2 is a vertical sectional view of the same structure,

Fig. 3 is an exploded isometric view of the major parts of the device ofthe preceding figures, a part being again broken away,

Fig. 4 is a plan View of the base member of the same embodiment, and

Fig. 5 is a fragmentary sectional view of a modified base member adaptedfor a single-winding coil.

Referring now to Figs. 1 to 4 of the drawings, there is shown a radiofrequency transformer adapted for use in radio apparatus working forexample in the ultra high frequency range of 240 megacycles, and whichapparatus is of very compact form. Units of this type, and their relatedsingle winding inductances, may be used as interstage transformers,modulation transformers, chokes and for a variety of other purposes. Inmost applications, the inductance and capacitance values associated withthe conductive leads from the coils may form an important part of thetotal circuit values, and it is hence essential that the disposition ofthese leads (and indeed of the turns forming the coils themselves) benot subject to uncontrolled variations, such as might occurinadvertently. Also, it is desirable that the adjustments of the tuningslug or core should remain as intended.

The unit illustrated in the drawings has these characteristics, and isformed practically entirely of molded parts which can be manufactured toclose tolerances without excessive cost. The invention provides aminimum number of different molded components, from which the differentrequired types of coils may be readily produced.

As shown in Figs. 1 to 3, the transformer coil form comprises as itsmain parts a body portion 10, a base member 12, a sleeve member 14 and acap member 16. The upper portion of the main body portion 10 is ofgreater diameter than the remainder, and is designated in Fig. 3 bynumeral 18, while the lower portion of smaller diameter is designated20. Both portions are bored axially, and the bore in the lower portion20 is sized to fit snugly upon the upwardly extending cylindrical boss22 of the base member 12. As assembled, these interfitting parts aresecured firmly together as by a small quantity of an adhesive for theparticular material of which they are made. Preferably, these parts (andthe other parts of the unit which are shown as insulating) are formed ofsuitable plastic having the desired electrical characteristics such ashigh insulating value and low dielectric loss.

The base member 12 is of generally disc-like configuration having theupstanding central boss as described. The upper surface of the body, asbest shown in Fig. 4, has an annular portion 24 against which the loweredge of portion 20 seats when assembled. Surrounding this annularshoulder is an annular groove 28 into which extends the winding carriedby the body portion of the form (see also Fig. 2), and a further annulararea 26 which constitutes the seat for an outer winding sleeve 14. Aplurality of slots 30 are cut into the under surface of the base 12,these providing passages through which the lower end of the conductorwound on body 20 may be brought out. The provision of a plurality ofthese grooves or slots 30 enables the use of the same form for differentwinding arrangements, such as windings having different fractionalturns, and also enables the terminal lead to be maintained in a desireddirection and position where it leaves the base.

The upper end of the conductor wound on the portion 20 is passed throughan apertured lug 32 integral with the body member 10, it beingunderstood that when the body and base are cemented together, theangular orientation of lug 32 with respect to the base may be positionedas required by the circuitry or chassis arrangements.

The cap member 16 may have an enlarged charnfered head portion as shown,and a cylindrical portion 34 extending downwardly therefrom, the wholehaving a threaded bore 36. As best shown in Fig. 2, the upper portion ofthe bore in body member 10 is similarly threaded, and the cylindricalportion 34 of the cap 16 is sized to fit loosely within the upper part18 of said body member 16. A spring washer 46 surrounds the cylindricalportion 34 and urges these parts away from one another, so that when thethreaded magnetic slug 48 is threaded into position as shown, thetension of spring washer 46 maintains a tight threaded fit for alladjust ments of the slug, and prevents casual disturbance of theadjustment. The under side of the head portion of cap 16 has a lug 38engageable in one or another of a plurality of slots 40 in the headportion of body member 10 to prevent relative rotation of the cap andbody member.

An apertured lug 50 is integral with the base member 12', andprovides ananchor for the lower end of" a conductor wound on the sleeve 14. Thissleeve is also cemented in place in the base member in the same manneras is the main body portion or member 1'6, and since the sleeve may haveany rotational position, the number of turns on this winding may beadjusted to the desired fraction. An apertured lug 62 integral withsleeve member 14 provides a top anchoring for the winding and leadtherefrom.

Depending from the under side of base member 3.2 is a boss 54 whichserves tomount the device upon a chassis plate or the like, as bypassing through a suitable hole in such plate. A retaining ring. 56(Fig. 2) is cemented onto the projecting end of this boss so as to clampthe assembly firmly in place. If required, as insulating washer 5d maybe inserted between the base 1.2 and chassis to ensure insulationbetweenv the winding on sleeve 14 and the chassis.

It will be seen from the above description that both the winding. 64 onbody portion 11) and the winding on sleeve 14 can be arranged so thattheir respective leads arrive and depart from the transformer in fixed,accurately defined directions, and that the entire device will berelatively free item random efiects due to vibration, shock or otheraccidental causes. The relative positions of the two windings in thedevice are also accurately maintained.

In a practical commercial embodiment of the unit as actuallymanufactured, the over-all height of the unit is of the order of A of aninch, so that the drawings are actually considerably enlarged. Even inthis small size, the parts have considerable and adequate strength andtheir design greatly simplifies winding and assembly.

in the modification shown in Fig. 5, which is adapted for a singlewinding, for example for use as a radio frequench choke, a slightlymodified base member 66 is employed. When a single winding 64 isrequired, the diameter of the base can be reduced somewhat, and thisembodiment uses a base member having an annular groove 58 to receive theend of the body member 16, and is equipped with an apertured anchoringlug 7 and fastener or mounting elements 72, 74 in a manner quite similarto that already described above. The parts are assembled with cement oradhesive as before to provide a unitary structure.

While the invention has been described in connection with certainpreferred embodiments, numerous minor changes and modifications may bemade without departing from the spirit of the invention as defined inthe appended claims.

What is claimed is:

l. A coil form comprising a base portion, a hollow body portion securedto said base portion, apertured lugs on both said portions, a hollow capportion loosely received in said body portion for axial movement withrespect to said body portion, said cap portion and said body portionbeing threaded internally on a common axis, a magnetic tuning slugthreadedly received in said cap portion and said body portion, andresilient means between said cap portion and said body portion forurging said portions away from one another to clamp said tuning slug inposition within said body portion.

2. The structure in accordance with claim 1, in which said base portionis slotted in a plurality of different directions, whereby awinding onsaid body portion may be brought out through said base portion in adesired direction.

3. The structure in accordance with claim 1, and a sleeve secured tosaid base portion and sized to define an annalar winding space betweensaid sleeve and said body portion.

4. The structure in accordance with claim 3, and an apcrtured lug onsaid sleeve.

5'. The structure in accordance with claim 1, and cooperating formationson said body portion and said cap portion for retaining the same againstrelative rotation, while permitting limited. axial movementtherebetween.

6. The structure in accordance with claim 1, in which said base portionhas a boss. extending therefrom in one direction to receive said bodyportion, and a boss extending therefrom in the opposite direction formounting said base portion upon a surface.

7. A coil form comprising a base, a body portion cemented to said baseat one end thereof, a cap portion loosely received in said body portionat its opposite end, a magnetic tuning slug threadedly engaging bothsaid portions, a spring between said portions for urging them axiallyrelative to one another to clamp said slug in fixed position, andcooperating formations on said portions for locking. them againstrelative rotation.

8. A coil form in accordance with claim 7, including anaperturedconductor-guiding lug extending outwardly from each of said base andsaid body portions.

References Cited in the file of this patent UNITED STATES PATENTS609,144 Goddin -Aug. 16, 1898 2,298,275 Bohren Oct. 13, 1942 2,375,309McCoy May 8, 1945 2,462,822 Wood Feb. 22, 1949 2,464,218 Di Vita ct al.Mar. 15, 1949 2,469,137 Strong May 3, 1949 2,581,165 Bonanno Jan. 1,1952 FOREIGN PATENTS 209,896 Switzerland Aug. 1', 1940 780,543 FranceFeb. 4, 1935

